/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;

import java.util.ListIterator;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An iterator that transforms a backing list iterator; for internal use. This avoids the object
 * overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class TransformedListIterator<F extends @Nullable Object, T extends @Nullable Object>
        extends TransformedIterator<F, T> implements ListIterator<T>
{
    TransformedListIterator(ListIterator<? extends F> backingIterator)
    {
        super(backingIterator);
    }

    private ListIterator<? extends F> backingIterator()
    {
        return Iterators.cast(backingIterator);
    }

    @Override
    public final boolean hasPrevious()
    {
        return backingIterator().hasPrevious();
    }

    @Override
    @ParametricNullness
    public final T previous()
    {
        return transform(backingIterator().previous());
    }

    @Override
    public final int nextIndex()
    {
        return backingIterator().nextIndex();
    }

    @Override
    public final int previousIndex()
    {
        return backingIterator().previousIndex();
    }

    @Override
    public void set(@ParametricNullness T element)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public void add(@ParametricNullness T element)
    {
        throw new UnsupportedOperationException();
    }
}
